Wind turbine blades for rotors of wind turbines have a length of about 40 meters or more, sometimes about 90 or 100 meters. The wind turbine blades need to be very stiff and, thus, usually constitute a shell structure comprising a metal or composite material. Such composite materials for wind turbine blades commonly consist of a plastic material that is reinforced with strong fibres such as glass fibres, carbon fibres or others. A growing number of such products are manufactured in a fibre reinforced thermoplastic material. For those products a mixed material of thermoplastic fibres and reinforcing fibres can be placed in a mould and melted by heating the mould. In the heated mould the thermoplastic matrix material melts and consolidates with the reinforcement fibres to form a strong composite material. For large structures with a high wall thickness or structures having an internal core structure, which itself is thermally insulating, it is however nearly impossible or at least time- and energy-consuming to heat up the material, especially the inner parts of the sandwich structure.
Therefore, thermoplastic materials are not common in products with higher wall thicknesses or having thermally insulating sandwich core materials such as balsa wood, honeycomb elements, PVC foam. Instead of the use of a thermoplastic material, a thermosetting polymer material such as polyester, vinyl ester or epoxy resin is commonly used in such composite materials (cf. WO 2010133587 A1).
Thermosetting composite materials have, however, several disadvantages such as high costs during the recycling of those materials or the accumulation of high amounts of waste if a recycling is not possible.